。
The flavor isn't inferior at all compared to Japanese rice.
Literal
Flavor [topic-は] Japan's rice [compared-to-に比べて] inferiority [topic-は] doesn't-exist.
遜色 ('inferiority, being inferior') paired with ない is the set phrase 遜色がない / 遜色はない ('is not inferior'). に比べて ('compared to') is a formal comparative built from 比べる ('to compare'). Note the is-not-a-thing shape: Japanese prefers stating inferiority as absent rather than directly asserting quality.